...

Start small, get it checked in (or patch submitted) and work iteratively.

Things that always need doing

• Final variables & fields are preferred where possible, but a lot of the code is old. Feel free to add them and hand the code back.
• If you have any skills with code coverage tools, then you'll probably find way too much to do! Tests are always welcome.
• There are over a 1,000 TODO comments in the code. Maybe some should be deleted. Maybe some could be completed. They probably all should have a JIRA id on them.
• Pick a random class, see if you can figure out what it is doing and javadoc it.
• Add @Override where applicable
• Intellij has an 'Inspect Code' feature. Yikes does it produce a lot of output.
• No doubt there is some exception handling that can be greatly improved.

Keep in mind people have to read and apply all these changes so resist the urge to fix everything everywhere and send huge patches. Fix a file or two and send it in as a patch and see what people think of the approach.

Things to avoid

Be careful with reformatting

Try to never mix logic changes with code reformatting. It makes it nearly impossible for others to see what the actual change was.

• If you are a committer and want to reformat something, do the reformat as a separate commit before or after the real change. As long as they are separate and clearly marked it should be easy for people to see what is going on.
• If you are a contributor and want to reformat something, maybe suggest it on the list, but avoid submitting patches that are just reformatting.